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→Underdrains for exfiltrating practices
==Underdrains for exfiltrating practices==
==Underdrains for exfiltrating practices==
The pipe within the drain should be elevated from the base to promote infiltration of the water stored beneath. The depth of this [[Bioretention: Internal_water_storage| internal water storage reservoir]] should be sized according to the desired [[drainage time]] and the [[design infiltration rate]] of the native soils below. An alternative design configuration permits the head of water to be stored by using an upturned outflow pipe.
The perforated pipe within the drain should be elevated from the base to promote infiltration of the water stored beneath. The depth of this [[Bioretention: Internal_water_storage| internal water storage reservoir]] should be sized to capture and infiltrate the design storm event runoff volume based on the desired [[drainage time]] and the [[design infiltration rate]] of the native soils below. An alternative design configuration is to install the perforated pipe on the base of the practice and using an upturned outflow pipe to permit the required head of water to be stored.
*At least one pair of vertical cleanout pipes/wells should be included in the design, for inspection and periodic flushing of accumulated sediment. As most push camera and hydro-jetting equipment used for this has some trouble negotiating 90 degree bends, it is preferable that 45 degree pipe couplings be used instead.
*Underdrain access structures, which may be maintenance holes or vertical standpipes connected to the perforated pipe, must be included in the design for periodic inspection and flushing. Negotiating 90 degree bends will be troublesome for most push camera and jet nozzle cleaning equipment, so it is preferable that 45 degree pipe couplings be used instead.
{| class="wikitable"
{| class="wikitable"
|+Clean out spacing<ref>Province of Ontario. (2018). O. Reg. 332/12: BUILDING CODE. Retrieved February 23, 2018, from https://www.ontario.ca/laws/regulation/120332</ref>
|+Clean out spacing<ref>Province of Ontario. (2018). O. Reg. 332/12: BUILDING CODE. Retrieved February 23, 2018, from https://www.ontario.ca/laws/regulation/120332</ref>